Carburetor



Sept. 13, 1966 w COOK L 3,272,487

CARBURETOR 5 Sheets-Sheet 1 Filed April 29, 1963 INVENTORS FORREST W.COOK JAMES T BICK'HAUS Sept. 13, 1966 F. w. COOK ETAL 3,272,487

CARBURETOR 5 Sheets-Sheet 2 Filed April 29, 1963 FIG.2.

Sept. 13, 1966 Filed April 29, 1963 F. w. COOK ETAL 3,272,487

CARBURETOR 5 Sheets-Sheet 5 a? I 70 m2 86 72 I M L FlG.4a.

Sept. 13, 1966 F. w. COOK ETAL CARBURETOR 5 Sheets-Sheet 5 Filed April29, 1963 United States Patent 3,272,487 CARBURETOR Forrest W. Cook,Webster Groves, Mo., James T. Bickhaus, Granite City, 111., and RobertJ. Smith, Florissant,

Mo., assignors to ACE Industries, Incorporated, New

York, N.Y., a corporation of New Jersey Filed Apr. 29, 1963, Ser. No.276,472 14 Claims. (Cl. 26139) This invention is directed to an airvalve carburetor of the type having an air and fuel mixture conduitthrough the carburetor body. Within the mixture conduit is mounted amanually operated throttle valve for movement between an open and closedposition. Upstream from the throttle valve is mounted within the mixtureconduit an air valve structure, which measure the flow of air throughthe carburetor to meter the fuel flowing to the engine. The presence ofthe air valve also provides a subatmospheric pressure in the region ofthe fuel nozzles to draw fuel into the mixture conduit.

In some air valve carburetors of this type, a servo motor positions theair valve in response to the air pressure drop across the air valve suchthat the angular position of the air valve is a measure of the air flowto the engine. The air valve is connected directly to a device formetering fuel to the engine so that fuel flow is provided which isproportional to the air flow to the engine. With the same amount of airflow through the engine, the air valve will assume the same angularposition and thus provide the same fuel metering, when the engine is hotas when it is cold. However, for satisfactory engine operation, theengine requires a richer air-fuel mixture when cold than when the engineis warm. It is thus necessary to vary the relationship between the airflow and fuel flow to the engine by providing means to change thisrelationship in response to engine temperature.

It is therefore an object of this invention to provide a novel air valvecarburetor of the type described in which the air valve is responsive toambient temperatures.

It is a further object of this invention to provide a novel carburetorhaving an air valve which closely follows changes in ambient temperatureto provide an optimum fuel and air mixture during engine operation.

The invention is one in which the position of the air valve of thecarburetor determines the fuel flow to the engine in proportion to theamount of air flowing to the engine. The position of the air valve iscontrolled by a servo motor. To change the relationship between the airflow and fuel flow to the engine, in response to engine temperature, theair pressure within the servo motor is varied by bleeding more or lessair to the servo motor in response to changes in the engine temperature.This changes the relationship between fuel flow and air flow to theengine as determined by the angular position of the air valve.

FIGURE 1 is a plan view partly in section of an air valve carburetorincluding the invention.

FIGURE 2 is a side view in elevation of the carburetor of FIGURE 1showing a portion of an air filter and an engine manifold to which thecarburetor is attached.

FIGURE 3 is a sectional view of the carburetor of FIGURE 1 along thelines 3-3.

FIGURE 4 is a sectional view of the carburetor of FIGURE 1 along sectionlines 4--4.

FIGURE 4a is an enlarged partial view of the fuel control metering rodof FIGURE 4.

FIGURE 5 is a sectional view of the carburetor of FIGURE 1 along lines55.

FIGURE 6 is a schematic view of the carburetor of FIGURES 1 through 5,showing the operation of the carburetor during cranking of the engine incold weather.

FIGURE 7 is a schematic view of the carburetor of 3,272,487 PatentedSept. 13, 1966 ice FIGURES 1 through 5, showing the operation of thecarburetor under cold ambient conditions.

FIGURE 8 is a schematic view of the carburetor of FIGURES 1 through 5,showing the operation of the carburetor during warm ambient conditions.

FIGURE 9 is a schematic operational view of the carburetor of FIGURES 1through 5 during wide open throttle operation under normal warm ambientconditions.

The carburetor shown in the figures has a body casting portion 10, whichis connected at a flanged end 12 to an intake manifold structure 13 ofengine E shown in FIG- URES 2 and 3. The other end of the carburetorbody support a cover casting 19 formed with an air horn section 14mounting an air filter 15, through which the air passes into thecarburetor. Passing through the carburetor body 10 from the air horn 14are a pair of air and fuel mixture conduits 16 and 17 each opening atone end into the intake manifold 13 at 18 and through which air from theair filter 14 passes to the engine. Mounted in the manifold ends of themixture conduits 16 and 17 are throttle valves 20 and 21, respectively,fixed to a common throttle shaft 22 journaled for rotational movement inappropriate bearing surfaces in the carburetor body 10. Fixed to one endof the throttle shaft 22 is a manually operably lever 24 (FIGURES 1 and4) for moving the throttles 20 and 21 from a closed to an open position.In the closed position, the throttles are across their respectivemixture passages 16 or 17, as indicated in FIGURES 3 and 5,. to preventthe flow of air therethrough. The throttles may be moved from thisclosed position to a wide open position schematically indicated inFIGURE 9.

Mounted upstream of the throttles 20 and 21 and across the air hornsection 14 of the carburetor is an air valve 26. As indicated in FIGURE1, valve 26 closes the air horn passage and extends across the twomixture passages 16 and 17. In this closed position, a flow of air maypass into the two mixture passages 16 and 17 through apertures 25 and 27in the air valve provided for the clearance of nozzle bars when the airvalve opens. Air valve 26 is fixed eccentrically to a shaft 28 journaledin the carburetory body for rotational movement. Shaft 28 extendsthrough the carburetor substantially parallel to the throttle shaft 22.

A short level arm 30 (FIGURES l and 3) is fixed to and extends from theair valve shaft 28. Lever arm 30 is loosely connected to one end of anactuating rod 32, the other end of which extends through a passage 33 inbody casting 10 and is fixed to a backing plate 34 of a diaphragmassembly 36 of a servo motor 39. The diaphragm assembly consists of aflexible diaphragm 38 of rubber or appropriate material, which has itscenter fixed between the pair of plates 34 and 35. The attached end ofoperating rod 32 may be spun over to lock the plates tightly togetherwith the diaphragm 38 in-between. The peripheral edge of diaphragm 38 issandwiched between the flange rim 40 of a spring cup housing 42. Rim 40is tightly fastened as by machine screws 41, for example, extendingthrough the housing flange 40 into the adjacent portion of thecarburetor body 10. A spring 44 is mounted within the housing 42 withone end abutting the closed end of the housing and its other end biasedinto contact with the center plate 35 of the diaphragm assembly. Spring44 biases the diaphragm assembly 30 in a direction to close the airvalve 26.

Diaphragm 38 forms a chamber 43 with cup housing 42 and a chamber 45with body casting 10. Chamber 43 is sealed except for an air passage 46extending through the wall and the flange 40 of spring housing 42 tojoin a second air passage 47 through the carburetor body. Air passage'47 connects into a branch passage 48 leading into the flange 12 of thecarburetor and connecting into the intake manifold at opening 51.Another branch 49 of fuel bowls.

passage 47 extends to a port 50 into the mixture conduit 17 between theclosed position of throttle valve 2 1 and the air valve 26.

Formed within the body 10 of the carburetor are a pair of fuel bowls 52and 54 (FIGURES 2 and 4) positioned adjacent to the mixing conduit 17. Afuel inlet passage 56 is formed through the body cover casting x19. As

shown in FIGURE 1, the fuel passage 56 extends the length of thecarburetor to provide fuel access to the two The fuel passage 56 isconnected in any appropriate manner to an inlet fuel line 58 leadingfrom a fuel pump 60 which provides fuel for the carburetor from 'thefuel tank 62. The fuel inlet line 58, fuel pump 60 and fuel tank 62 areonly schematically shown in FIG- URE 1.

Fuel from fuel passage 56 enters each fuel bowl through a short passage61 having a valve seat, which is controlled by a needle valve 63operated from a float lever 64 pivoted within the fuel bowl at 66 andhaving a free end attached to a float 68. The float controlled inletneedles 63 operate in a well-known manner. As the fuel in bowls 52 and54- reaches a predetermined level, the floats 68 through levers 64 willforce the pointed end of needles 63 into the valve seats to preventadditional flow of fuel into the bowls, respectively.

In the bottom of each fuel bowl there is threaded a fuel jet 70 having acalibrated passage therethrough connected to a fuel passage 72 leadingto a respective fuel well 74 or 75 (FIGURES 1 and formed in thecarburetor body and in the wall of each of the mixing conduits 16 and17, respectively. For example, in FIGURE 1, well 74 is indicated asbeing adjacent to the mixing conduit 16, and

75 is adjacent to mixing conduit 17. FIGURE 5 shows the well 75 and mainfuel nozzle construction associated 'with mixing conduit 17, which isidentical to similiar structure associated with mixing conduit 16.

Mounted in the top of each one of the mixing conduits 16 and 17 is aseparate subassembly insert 76 consisting 'of a pair of fuel tubes andthe main nozzle structure. As shown in FIGURE 5, each subassemblyconsists of a block 78 having a tubular cross member 80 formed with amain fuel passage 82 and an idle fuel passage 84. Nozzle ports with thefuel passage 84. Fuel tubes 88 are closed except for small restrictionsat their lower ends suspended Within the fuel wells 74 and 75,respectively. Short tubes 85 are press-fitted into the opposite side ofblocks 78 to form fuel passages leading from passages 84 across passages82 into respective idle chambers 87. Idle chambers 87 open through ports95 upstream of throttle and 2. 1, respectively. Short passages 93connect idle chambers 87 to idle ports 97 opening downstream ofthrottles 20 and 21,

respectively. Idle air and fuel flow through ports 97 is controlled byan idle adjusting screw 101.

Restrictions 89 of predetermined size form air bleed passages from theair horn section into air passages 90 leading into the upper portion ofeach well 74 and 75 to provide air flow into the main fuel passages. Airpassages 91 extend from the upper end of the air horn through the fuelbowl cover casting .19 into air passages 92, each respectively connectedto tube 85 and idle fuel passage 84. A restricted portion 94 in eachpassage 92 and restrictions 81 connecting idle passage 84 to the airhorn 14 control the amount of air bled into the idle system.

Within each fuel bowl there is mounted a fuel metering rod 96 which isconnected at an upper end to a lever 99 fixed to the portion of airvalve shaft 28 extending over the top of the respective fuel bowl. Theother end of each metering rod 96 has variations in rod thickness, asshown in FIGURE 4a, consisting of an end portion 99 of minimumthickness, a tapered portion 103, an intermediate portion 100 of maximumthickness and a second tapered portion 102 of thickness varying fromthat of portion 100 to a minimum thickness of portion 105. Theconnection of metering rods 96 to the air valve shaft 98 providessimultaneous operation of the metering rods with the air valve.

A lever 104 (FIGURE 2) is fixed to the end of throttle shaft 22 oppositeto that carrying throttle lever 24. Lever 104 carries a spring biasedscrew 104 for contacting a fast idle cam 106 freely pivoted on a shaft108 and in an eccentric manner so that gravity will bias the cam 106 ina counterclockwise direction, as viewed in FIGURE 2. A second lever 110is also freely mounted for rotation on screw shaft 108 and is connectedby a link 112 to a control lever 114 fixed to a shaft 116 journaled forfree rotation in a cup housing 118, as shown in FIGURES 1 and 2. Controllever 114 is also connected by a link 119 to a lever 120 loosely mountedfor rotation at one end of valve shaft 28. Fixed at the end of the airshaft 28 for rotational movement therewith is a short lever 122 having aportion 124 extending over the lever 120.

In accordance with this invention, there is fixed to an intermediateportion of shaft 116 and for rotation therewith, a second lever 126carrying at its free end a tapered metering valve 128. The upper end ofvalve 128 is pivotally mounted on the free end of lever 126 so as tomove relative thereto. The tapered end of the metering valve 128 extendsinto a restriction 130 having a passage therethrough of predeterminedsize which leads into an air chamber 132 in the housing 118. Air chamber132 is connected by an air passage 134 to short passage 136 joined tothe air passage 47, as shown in FIG- URE 3, and schematically indicatedin FIGURES 6 through 9. A third lever 138 is fixed at the other end ofthe shaft 116 for rotation therewith. Lever 138 is forked at its freeend 140 to receive one end of a bimetallic thermostatic spring 142fitted into the fork 140 so as to move lever 138. This connection isschematically shown in FIGURES 6 through 9. The outer end of spring 142is fixed to a stationary shaft 143 mounted on the cup housing 118.

The cup housing 118 is divided into a pair of chambers 145 and 146 by animperforate wall structure 144 extending transversely across thehousing. This wall 144 prevents the interference of air flow through onechamber With the air flow conditions of the other chamber. Chamher 145is connected to the atmosphere through a vent schematically indicated at147 in FIGURES 6 through 9. Chamber 146 is connected to a source ofheated air such as a stove connected to the exhaust manifold of theengine. Air from the stove is brought through the hot air conduit andthrough an inlet fitting 48 into the chamber 146. Chamber 146 isconnected by a double branched air passage 149 to the carburetor flange13 at points downstream of the throttles 20 and 21, respectively. Thisis schematically shown in FIGURES 6 through 9 and in specific detail inFIGURE 3.

Because of subatmospherie air pressure conditions in the manifold 18during engine operation, air will flow from the manifold stove throughthe hot air conduit and fitting 148 into the chamber 146 and from thechamber through passage 149 into the manifold. Also, when the valve 128is open, atmospheric air will flow through vent 147 into chamber 145 andfrom chamber 145 through passages 132, 134 and 136 into passage 47.

An accelerating pump piston 150 is mounted within a pump cylinder 152(FIGURES 4 and 6) formed at the end of the fuel bowl 54. A one way ballcheck valve 154 permits fuel to flow from the fuel chamber into the pumpcylinder 152. The piston rod 156 is connected by a linkage -158 pivotedon the cover casting 19 through a link 160 to the throttle lever 24. Theaccelerating pump provides additional fuel during the opening of thethrottle. When the throttle is opened, the pump piston 150 is presseddownwardly to force fuel through an accelerating fuel passage 162connected to accelerating nozzles 164 (FIGURES and 6) extending intoeach of the mixture conduits 16 and 17. This provides additional fuelduring throttle operation.

In operation, the engine is cranked to operate the fuel pump and toforce fuel into the inlet passage 56 of the carburetor. With the floatvalves 63 in a lowered position, fuel will flow from fuel passage 56into each of the fuel bowls 54 and 52. Fuel will continue to flow untilthe floats 68 are raised to a predetermined position at which point theneedle valves 63 are closed to prevent further flow of fuel into thefuel bowls. Fuel will flow from each bowl by gravity through thecorresponding metering jet 70 into fuel passages 72 and to a level ineach of the fuel wells 74 and 75 equal to the level of fuel in therespective fuel bowl. Fuel will also flow past the check valve 154 tofill the accelerating pump cylinder 152 to the level of fuel in the fuelbowl.

One side of diaphragm 36 of servo motor 39 is exposed to air pressurewithin chamber 44, which is connected to port in mixture conduit 17between air valve 26 and throttle valve 21. The other side of diaphragm36 is exposed through passage 33 to substantially atmospheric airpressure in the air horn 14 upstream of air valve 26.

Starting During cranking of the engine with the throttle open, theengine turns over to pump air through the carburetor to start theengine. With the engine cold, spring 44 of the servo motor holds airvalve 26 closed. Servo motor spring 44 also biases the metering rods 96through levers 98 to their uppermost position, so that the smalldiameter starting portions 99 of the metering rods are respectivelypositioned within the metering jets to enable a sufficient amount offuel to flow into the fuel nozzles 80. Sufficient air to start theengine passes through apertures 25 and 27 in the air valve 26 and intothe mixture passages 16 and 17, respectively. Fuel to start the engineis drawn out of the fuel wells and the nozzle bar passages 82 and 84 bythe manifold vacuum extending upstream of the open throttles to thenozzle lbars 80. This fuel passes into the mixture conduits through themain nozzle ports 83 and the idle ports and 97.

Engine operation When the engine is running and the throttles are openedfrom their closed positions, the air pressure at port 50 drops fromatmospheric and the air pressure in motor chamber 43 is reduced untildiaphragm 36 is pressed inwardly against the bias of spring 44. The airvalve 26 then takes a position determined by servo motor 39, in whichthe difference in air force on the opposite sides of diaphragm 36balances the bias of spring 44. As throttles 20 and 21 are moved tochange the amount of air flowing to the engine, the servo motor 39 willchange the position of air valve 26 to retain substantially the samepressure drop across the air valve. The air valve 26 is thus a devicefor measuring air flow through the carburetor to the engine.

The value of spring 44 is selected to retain a fixed pressure dropacross the air valve at all times. This spring sets the angular positionof the air valve relative to the amount of air flowing through thecarburetor This then positions the proper portions of metering rods 96Within jets 70. The shape of metering portions of rods 96 are calibratedto give sufficient fuel flow through jets 70 to provide maximum power atany speed of the engine at Wide open throttle up to the full air flowcapacity of the carburetor.

The tapered portions 102 of metering rods 96 are shaped to provide anincreasing flow of fuel through jets 70 as the air valve opens from apartially open position to full open position, at which opening of theair valve, the rod portions 105 are within jets 70 for maximum fuel how.The optimum air-fuel ratio is maintained with a full open air valve bythe increased depression around the nozzle bars 80 due to increasedmanifold vacuum at higher speeds. The tapered metering rod and itsc-oaction with the air valve as just described is the invention of JamesT. Bickhaus and Forrest W. Cook which invention is being claimed incopending application Serial No. 293,411 filed July 8, 1963.

The air valve opening and metering rod position for a given air flowthrough the carburetor at wide open throttle operation will not providethe proper air-fuel mixture at part open throttle with minimum loads. Itis thus necessary to change the relationship between the air flowthrough the carburetor and the flow of metered [fuel to the engine, sothat less fuel will flow during part throttle minimum load conditionsthan during wide open throttle maximum power conditions positionedwithin the jet. To obtain economy during part throttle operation of theengine, the air bleed passage 48,. connecting air passage 47 to a port51 in the mixture passage 17 downstream of throttle 21, reduces the airpressure in passage 47 and motor chamber 43. This opens the air valve 26slightly more against spring 44. The air pressure in the region of thenozzle bars 80 is thus increased, which reduces fuel flow from thenozzle apertures 83 to produce a leaner air-fuel mixture to the engine.Although opening of the air valve in this manner increases the openareas between the rod portions 102 and jets 70, the increase of airpressure around the nozzle bars 80 has the controlling effect on fuelflow under the conditions described. Air bleed 48 is only effectiveunder conditions of high manifold vacuum operation of the engine wheneconomy of operation is desirable at low speeds or minimum loadconditions. To provide the desired increase in the opening of air valve26 under these conditions, a restriction 170 is placed in the bleedpassage 48. The size of the orifice in restriction 170 is preselected togive the desired effect. In the carburetor mentioned above of the typedescribed, a restriction of 0.035 inch was used. This opening sizeprovided a correction to the position of the air valve proportional tothe vacuum changes downstream of the throttles.

Cold engine operation When ambient conditions are below a temperature ofabout 75 F., the thermostatic spring 142 biases lever 138, shaft 116 andlever 114 in a clockwise direction to a position shown in FIGURES 2 and6. In this position, operating lever 114 and link 112 have moved thefast idle cam 106 in a clockwise direction against gravity bias by theaid of a lug 109 fixed to lever 110 in the path of rotation of cam 106.After the engine has started and the throttle lever 24 manuallyreleased, the adjustment screw stop 104 on the throttle lever 104 willcontact the high portion 107 of the cam 106 and hold the throttles in aslightly open position so that the engine will operate at a fast idlespeed (FIGURE 7).

The idle speed of the engine provides a subatmospheric pressure withinthe intake manifold opening 18 in the order of 18 to 20 inches ofmercury negative pressure. This negative pressure will be effectiveupstream of throttles 20 and 21 to cause a depression below air valve26. This low pressure will be sensed through port 50 and passage 47 tothe servo motor 39, which will operate to partially open the air valve26 and permit flow of suflicient air past throttles 20 and 21 for thecold idle operation.

Idle fuel is drawn from the nozzle ports 83. Also,

air passing through apertures 25 and 27 will sweep around the upperedges of the slightly opened throttles 20 and 21 and will draw air andfuel from the idle ports 95. Idle fuel from idle fuel passage 84 mixeswith air bled through passages 90, 91 and 92 and passes through tubes 85into idle chambers 87 and is drawn out through idle ports 97. Additionalair flows through the bypass passages 163 to enter the mixture conduitsbelow the throttles. The metering rod portions 103 are positioned withinjets 70 during this cold engine idling operation.

For satisfactory operation, the engine requires a richer air-fuelmixture than when the engine is warm. In accordance with our invention,the air pressure in servo motor 39 is changed in response to enginetemperature to provide a richer air-fuel mixture ratio for cold engineoperation. When the engine is cold, shaft 116 is biased by spring 142 toa position shown in FIGURES 2 and 6. In this position the metering valvepin 128 is moved out of the restriction 130 to permit a bleeding of airthrough passage 134 to passage 47 and through passage 49 to the mixtureconduit. This air bleed slightly increases the pressure within the servomotor chamber 43 which, with the spring 44, closes the air valve 26slightly from a position it would otherwise have. This results in ahigher depression in the area between the air valve and throttles 20 and21, which induces a richer fuel flow from the nozzle ports 83 andoptimum engine performance for cold engine operation. The amount thatvalve 26 is closed by the air bled through passages 134 and 136 may beadjustably controlled by the size of a restriction 135 placed in passage47 between passages 134 and passage 49. This restriction may be in therange of 0.025 to 0.040 in diameter in a carburetor of the typedescribed to provide the desired effect.

During engine operation, because of the subatmospheric pressure in themanifold inlet 18, there is a continuous flow of air from the exhaustmanifold stove through the housing chamber 146 and passages 149 which isdirected upwardly against throttles 20 and 21, respectively. When theengine begins to run, the air in the exhaust manifold stove becomesheated and the flow of air into the housing chamber 1146 becomes warm.The heated air in housing chamber 146 warms the thermostatic c-oil 142and causes it to relax and to move the lever 138 in a counterclockwisedirection from the position of FIGURE 6. This rotates shaft 116 andlever 126 so as to move the metering valve pin 128 into the passage ofrestriction 130.

As coil 142 is increasingly heated, the valve 128 progressively cutsdown bleeding of air through passage 134 so that pressure in motorchamber 43 decreases and motor 139 slowly moves air valve 26 fartheropen from its position determined by the air flow through thecarburetor. This lowers the depression of air pressure in the region ofthe nozzle bars 80 and lessens the flow of fuel from the nozzleapertures 83 to provide a leaner air-fuel mixture. Further heating ofthe coil 142 provides an additional counterclockwise movement of themetering pin 128 until it seats within the passage of restriction 130 toprevent all flow of air through passage 134 to passage 147, at whichtime the engine has reached a normal operating temperature. With airpassage 134 closed, pressure within servo motor 43 drops to a valuesensed by ports 50 and 51 alone. Air valve 26 now takes a part openposition determined by a predetermined pressure drop across the airvalve. This pressure drop can be preselected to retain the optimum flowof fuel from nozzle apertures 83 during warm engine operation with apart open throttle. In the carburetor mentioned above, of the typedescribed, spring 14 is selected to provide a constant pressure drop of0.3 inch of mercury across the air valve.

'When the engine has warmed to a normal operating temperature asdescribed, thermostatic spring 142 rotates shaft 116 and levers 114 and110 to their positions 8 indicated in FIGURE 8. When the throttles arenow operated, the idle stop screw releases the fast idle cam 106 andpermits it to drop by gravity. If the throttles are subsequentlyreleased for idling conditions, the screw 105 will contact the lowestcam position 113 (FIG- URE 2) and allow the throttles to take asubstantially closed position. Idle fuel is now drawn by manifold vacuummainly from the idle chambers 87 through the idle ports 97 and in themanner described above. Air flows through idle bleeds 81 and 91 and thebypass passage 163, controlled by the adjustment screw 165.

The rotation of shaft 116 counterclockwise by spring 142 rotatesoperating lever 114 to its fullest extent in the counterclockwisedirection (FIGURE 8). In this position, the pivot 115 between levers 114and 119 has passed over center of a straight line between shaft 116 andthe pivot 117 between levers 119 and 120. A toggle link is formed bylevers 114 and 119. This over-center toggle condition retains the lever120 in an uppermost position, as viewed in FIGURE 8, where lever arm 124will strike lever 129. This blocks open the air valve 26 and prevents itfrom closing as long as the engine is hot. Thus, the engine can bestarted without an overrich condition which would be provided with airvalve 26 closed. An optimum opening for valve 26 for hot engine startingconditions is from 25 to 30 degrees from its closed position. Also,holding the valve 26 in this open condition allows the engine when warmto function properly during idle operation when Warm without anover-rich fuel mixture. In this blocked open position of the air valve,metering rod portions 100 are positioned within jets 74 to provide asuflicient flow of fuel to the engine, during low speed or idlingoperation.

As the engine cools when not running and the thermostatic spring 142tensions, the lever 114 will be rotated clockwise and will break thetoggle stop. The air valve is then closed slowly as lever 121i is slowlyrotated clockwise by the cooling spring 142. When cold, the air valve 26is closed and in position for a cold start, as described above. Thetoggle mechanism and associated linkage just described is furtherdisclosed and claimed in copending application Serial No. 281,175, filedMay 17, 1963 for Robert J. Smith.

An additional bypass passage 172 may be used extending from the air horn14 to a port 174 in the mixture conduit 17 downstream of the throttle21. In cold engine operation passage 172 is closed, as shown in FIGURE6, by a valve 176 controlled by a bimetal, temperature responsive spring178. During hot ambient conditions spring 1'73 opens valve 176 and aircan flow through passage 172 to lean out the idle mixture in themanifold.

We claim:

1. A carburetor for an internal combustion engine, said carburetorcomprising a body structure having an air and fuel mixture conduittherethrough, a throttle valve mounted across said mixture conduit formovement from an open to a position closing said mixture conduit, meansfor operating said throttle valve, an air valve mounted within saidmixture conduit anteriorly of said throttle valve for movement from anopen to a position closing said mixture conduit, said body structurehaving a fuel chamber therein and a fuel passage extending from saidfuel chamber to said mixture conduit for supplying fuel thereto, saidpassage having a metering restriction, a metering rod operativelyconnected to said air valve, said metering rod having a portion ofvarying thickness within said metering restriction to vary fuel flowthrough said fuel passage, a servo motor responsive to ambient airpressure connected to said air valve to control said air valve, meansforming a first air passage to said servo motor from said mixtureconduit downstream of said air valve to expose said servo motor tochanges in air pressure in said mixture conduit in response to operationof said throttle, means forming a second air passage from ambient air tosaid first air passage, and

temperature responsive valve means in said second air passage forcontrolling the flow of air through said second passage whereby tomodify the operation of said servo motor in response to enginetemperatures.

2. The invention of claim 1 wherein said temperature responsive valvemeans includes a valve seat in said second passage, a valve membermounted for movement onto said valve seat to close said second passageand a bimetallic element connected to said valve member to move saidvalve member in response to ambient temperature.

3. The invention of claim 2 including means for directing engine heataround said bimetallic element.

4. The invention of claim 2 including a housing enclosing saidbimetallic element, and a conduit means connecting said housing to saidmixture conduit downstream of said throttle, said housing including aportion having an air passage opening into said housing and adapted tobe connected to a source of engine heated air.

5. A carburetor comprising a body structure having an air and fuelmixture conduit therethrough, a throttle valve mounted across saidmixture conduit for movement from an open to a position closing saidmixture conduit, means for operating said throttle valve, an air valveeccentrically mounted within said mixture conduit anteriorly of saidthrottle valve for movement from an open to a position closing saidmixture conduit, biasing means for biasing said air valve toward aclosed position, an air motor connected to said air valve to move saidair valve, said body structure including a first air passage from saidmixture conduit downstream of said throttle valve to said air motor anda branch passage communicating with said mixture conduit above saidthrottle valve whereby to control said air valve in response to pressuredrop across said throttle valve, means forming a second air passageconnected at one end to said first air passage and open at the other endthereof to ambient air, valve means for controlling flow of air throughsaid second air passage to said first passage, said valve meansincluding a valve seat Within said second passage and a valve structurefor closing said valve seat, temperature responsive means for operatingsaid valve structure and including a housing, a shaft rotatably mountedin said housing, said valve structure fixed to said shaft for rotationtherewith, and a bimetallic thermal sensitive spring having one endfixed within said housing and the other end thereof fixed to said shaftto operate said valve member in response to changes in ambienttemperature.

6. The invention of claim 5 including means for heating said bimetallicspring relative to engine operation to close said second air passage.

7. The invention of claim 5 including means for heating said bimetallicspring with engine heat.

8. The invention of claim 5 including means for conducting engine heatedair through said housing to heat said bimetallic spring.

9. A carburetor for an internal combustion engine, said carburetorcomprising a body structure having an air and fuel mixture conduittherethrough, a throttle valve mounted across said mixture conduit formovement from an open to a position closing said mixture conduit, meansfor operating said throttle valve, said 'body structure having a fuelchamber therein and a fuel passage extending from said fuel chamber tosaid mixture conduit for supplying fuel thereto, said passage having ametering restriction, a metering rod having a portion of differingthickness within said metering restriction to vary fuel flow throughsaid fuel passage, an air valve mounted within said mixture conduitanteriorly of said throttle valve for movement from an open to aposition closing said mixture conduit, an air motor responsive to airpressure connected to said metering rod and said air valve to move saidmetering rod portion and said air valve simultaneously, means forming anair passage to said air motor from said mixture conduit to expose saidair motor to changes in air pressure in said mixture conduit in responseto operation of said throttle, and temperature responsive means formodifying the air pressure in said passage to vary the position of saidmetering rod within said metering restriction in accordance withtemperature changes.

10. A carburetor comprising a body structure having an air and fuelmixture conduit therethrough, a throttle valve mounted across saidmixture conduit for movement from an open to a position closing saidmixture conduit, means for operating said throttle valve, an unbalancedair valve mounted within said mixture conduit anteriorly of saidthrottle valve for movement in response to air flow from a positionclosing said mixture conduit to an open position, a spring connected tosaid air valve and biasing said air valve toward a closed position, saidbody structure having a fuel chamber therein and a fuel passageextending from said fuel chamber to said mixture conduit for supplyingfuel thereto, said passage having a metering restriction, a metering rodoperatively connected to said air valve, said metering rod having aportion of varying thickness within said metering restriction to varyfuel flow through said fuel passage, an air motor connected to said airvalve, means forming air passages from said mixture conduit on bothsides of the closed position of said throttle valve to said air motor toposition said air valve against the bias of said spring in response topressure drop across said throttle valve, and temperature responsivemeans to modifying the air pressure effective on said air motor toposition said air valve in accordance with temperature changes.

11. A carburetor comprising a body structure having an air and fuelmixture conduit therethrough, a throttle valve mounted across saidmixture conduit for movement from an open to a position closing saidmixture conduit, a lever connected to said throttle valve for movementtherewith, an air valve mount-ed within said mixture conduit anteriorlyof said throttle valve for movement from an open to a position closingsaid mixture conduit, an air motor connected to said air valve to movesaid air valve, said body structure including a first air passage fromsaid mixture conduit downstream of said throttle valve to said air motorto control said air valve in response to pressure drop across saidthrottle valve, means forming a second air passage connected at one endto said first air passage and open at the other end thereof to ambientair, valve means for controlling flow of air through said second airpassage to said first passage, said valve means including a valve seatwithin said second passage and a valve movable onto and off said valveseat, engine temperature responsive means for operating said valvewhereby to modify the action of said air motor, a housing, a shaftrotatably mounted in said housing, said valve fixed to said shaft forrotation therewith, a bimetallic thermal sensitive spring having one endfixed within said housing and the other end thereof fixed to said shaftto move said valve onto said valve seat in response to changes in enginetemperature, a fast idle lever rotatably mounted on said carburetor inthe path of movement of said throttle lever, said fast idle lever havinga plurality of stop portions of successively increasing heights to holdsaid throttle at correspondingly more open positions for varying thespeed of engine idle operation, and linkage means connecting said fastidle lever with said shaft for movement therewith in response to enginetemperature.

12. The invention of claim 11 wherein said shaft positions said fastidle lever with a low stop portion thereof in the path of said throttlelever when said valve is on said valve seat.

13. The invention of claim 11 wherein said shaft positions said fastidle lever with a high stop portion thereof in the path of said throttlelever when said valve is off said valve seat.

14. A carburetor comprising a body structure having an air and fuelmixture conduit therethro'ugh (1) a throttle valve mounted across saidmixture conduit for movement from an open to a position closing saidmixture conduit,

(2) means for operating said throttle valve (3) an air valveeccentrically mounted within said mixture conduit anteriorly of saidthrottle valve for movement from an open to a position closing saidmixture conduit (4) an air motor connected to said air valve (5) biasingmeans for biasing said air valve toward a closed position (6) said 'bodystructure having a fuel chamber therein and a fuel passage extendingfrom said fuel chamber to said mixture conduit for supplying fuelthereto (7) said fuel passage having a metering restriction (8) ametering rod connected to said air valve for movement therewith, saidmetering rod having a portion of differing thickness within saidmetering restriction to vary fuel through said fuel passage (9) saidbody structure further including a first air passage from said mixtureconduit downstream of said throttle valve to said air motor and a branchpassage communicating with said mixture conduit above said throttlevalve whereby to control said air valve in response to pressure dropacross said throttle valve (10) means forming a second passage connectedat one end to said first air passage and open at the other end thereofto ambient air (11) valve means for controlling flow of air through saidsecond passage to said first passage whereby to modify the action ofsaid motor (12) said valve means including a valve seat within saidsecond passage and a valve member for closing said valve seat (13)temperature responsive means for operating said valve member andincluding a housing (14) a shaft rotatably mounted in said housing (15)said valve member fitted to said shaft for rotation therewith (16) and abimetallic thermo-sensitive spring having one end fixed within saidhousing and the other end thereof fixed to said shaft to operate saidvalve member in response to changes in ambient temperature.

References Cited by the Examiner UNITED STATES PATENTS 1,855,383 4/1932Capell 261-50 1,991,804 2/1935 Johnson 261-50 2,979,047 4/1961 Rappleanet a1. 261-39 X 2,996,051 8/1961 Mick 261-39 X 3,013,777 12/1961 White261-50 X 3,023,744 3/1962 Mick 261-39 X 3,081,984 3/1962 Wise 261-39 X3,107,680 10/1963 Thorburn 236-87 X 3,171,868 3/1965 Hamilton 261-39FOREIGN PATENTS 718,381 11/1954 Great Britain.

HARRY B. THORNTON, Primary Examiner.

T. R. MILES, Assistant Examiner.

1. A CARBURETOR FOR AN INTERNAL COMBINATION ENGINE, SAID CARBURETORCOMPRISING A BODY STRUCTURE HAVING AN AIR AND FUEL MIXTURE CONDUITTHERETHROUGH, A THROTTLE VALVE MOUNTED ACROSS SAID MIXTURE CONDUIT FORMOVEMENT FROM AN OPEN TO A POSITION CLOSING SAID MIXTURE CONDUIT, MEANSFOR OPERATING SAID THROTTLE VALVE, AN AIR VALVE MOUNTED WITHIN SAIDMIXTURE CONDUIT ANTERIORLY OF SAID THROTTLE VALVE FOR MOVEMENT FROM ANOPEN TO A POSITION CLOSING SAID MIXTURE CONDUIT, SAID BODY STRUCTUREHAVING A FUEL CHAMBER THEREIN AND A FUEL PASSAGE EXTENDING FROM SAIDFUEL CHAMBER TO SAID MIXTURE CONDUIT FOR SUPPLYING FUEL THERETO, SAIDPASSAGE HAVING A METERING RESTRICTION, A METERING ROD OPERATIVELYCONNECTED TO SAID AIR VALVE, SAID METERING ROD HAVING A PORTION OFVARYING THICKNESS WITHIN SAID METERING RESTRICTION TO VARY FUEL FLOWTHROUGH SAID FUEL PASSAGE, A SERVO MOTOR RESPONSIVE TO AMBIENT AIRPRESSURE CONNECTED TO SAID AIR VALVE TO CONTROL SAID AIR VALVE, MEANSFORMING A FIRST AIR PASSAGE TO SAID SERVO MOTOR FROM SAID MIXTURECONDUIT DOWNSTEAM OF SAID AIR VALVE TO EXPOSE SAID SERVO MOTOR TOCHANGES IN AIR PRESSURE IN SAID MIXTURE CONDUIT IN RESPONSE TO OPERATIONOF SAID THROTTLE, MEANS FORMING A SECOND AIR PASSAGE FROM AMBIENT AIR TOSAID FIRST AIR PASSAGE, AND TEMPERATURE RESPONSIVE VALVE MEANS IN SAIDSECOND AIR PASSAGE FOR CONTROLLING THE FLOW OF AIR THROUGH SAID SECONDPASSAGE WHEREBY TO MODIFY THE OPERATION OF SAID SERVO MOTOR IN RESPONSETO ENGINE TEMPERATURES.